I think Burger tuning had a test on all intake,
and result was no gain on any of aftermarket stuffs.
I think drop in filter is a good to have item (no change needed.. same time BMW has wonderful maintance plan where you dont pay for them anyways.)

I bought a drop in K and N filter for my 2012 535i. And when I went to the dealer to ask about something unrelated I told the service guy I installed the K and N. He said he didn't recommend them because the oil from the filler can mess up a sensor in the airbox. He said he has seen it happen several times. He didn't seem like the SA that hates modes. Quite the opposite. So I took it out and put the stock one back in.

Anyone heard about that ? It kind of makes sense. The K and N is kind of oily when I removed it from its box.

I bought a drop in K and N filter for my 2012 535i. And when I went to the dealer to ask about something unrelated I told the service guy I installed the K and N. He said he didn't recommend them because the oil from the filler can mess up a sensor in the airbox. He said he has seen it happen several times. He didn't seem like the SA that hates modes. Quite the opposite. So I took it out and put the stock one back in.

Anyone heard about that ? It kind of makes sense. The K and N is kind of oily when I removed it from its box.

Take what you hear from an SA with again of salt. If you want accurate information speak to the guys who actually work on the cars not the middleman between the tech and the owner.